Characteristics of streamer propagation along insulation surface: influence of shed configuration

The reasonable shed configuration could improve flashover voltage of insulator and enhance the reliability of the overhead transmission lines. An investigation into the effect of shed configuration on streamer propagation along insulation surface was presented. In the three-electrode arrangement, the influences of the diameter, location, and combination of insulator shed on streamer propagation path, propagation probability, 'stability' field, together with velocity, were measured using three photomultipliers and an ultraviolet camera. The streamer propagated along smooth insulation surface with two propagation paths. That is 'fast' component propagating along the insulation surface and 'slow' component propagating in air. As a shed appeared on the insulation surface, the 'fast' propagation path was cut off, and the 'fast' component of streamer never reached the cathode. The 'slow' propagation path could bypass the shed, and the 'slow' component of streamer would cross the gap to reach the cathode. Furthermore, the electric field required for streamer propagation along the insulator with a shed was larger than along the smooth insulator. The electric field required for streamer stable propagation was in proportion to the diameter of shed. Under the same electric field, the streamer propagation velocity was in inverse proportion to the diameter of shed. The location of shed also had a great influence on the characteristics of streamer propagation. The more the shed was close to the initiation of streamer, the more difficult the streamer propagated along the insulator surface.